June 15, 2004Open Access
View Full PaperUnderestimation of the Early Risk of Recurrent Stroke
Key Result
The 90-day risk of recurrent stroke was 14.5% to 18.3% when defined as any stroke ≥24 hours post-incident, compared to 4.8% to 5.9% when restricted to events ≥28 days post-incident.
Study Design
Type
Cohort (n=657)
Multicenter
Yes
Structured PICO
How do different definitions of recurrent stroke affect the estimated 90-day risk of recurrence in patients with incident ischemic stroke?
P
Population
657 patients with incident ischemic stroke from 2 population-based cohorts (Oxford Vascular Study [OXVASC] and Oxfordshire Community Stroke Project [OCSP])
I
Intervention
Definition A for recurrent stroke (any stroke >=24 hours after the incident event excluding early deterioration not caused by a stroke)
C
Comparator
Definition B (excluding any stroke within 21 days in the same territory as the incident event) and Definition C (any stroke >=28 days after the incident event)
O
Outcome
90-day risk of recurrent strokehard clinical
Restrictive definitions of recurrent stroke that exclude early events significantly underestimate the 90-day risk of recurrence, highlighting the need for a standardized, inclusive definition.
Abstract
BACKGROUND: There is considerable variation in the definitions used for recurrent stroke. Most epidemiological studies exclude events within the first 28 days (eg, Monitoring Trends and Determinants in Cardiovascular Disease MONICA) or events within 21 days in the same territory as the presenting event (eg, most stroke incidence studies). However, recurrence is most common during this early period and these restrictive definitions could underestimate the benefits of early prevention. METHODS: We determined the 90-day risk of recurrence after incident ischemic stroke in 2 population-based cohorts (Oxford Vascular Study OXVASC and Oxfordshire Community Stroke Project OCSP) with the 3 most common definitions: any stroke > or =24 hours after the incident event excluding early deterioration not caused by a stroke (definition A); as above, but excluding any stroke within 21 days in the same territory as the incident event (definition B); and any stroke > or =28 days after the incident event (definition C). RESULTS: 657 patients had 93 recurrent strokes between 24 hours and 90 days after the incident event. The 90-day recurrence risks (95% CI) using definition A were 14.5% (11.5 to 17.5) in the OCSP and 18.3% (10.8 to 25.8) in the OXVASC. The equivalent risks using definitions B and C were 8.3% (5.9 to 10.8) and 4.8% (2.8 to 6.7), respectively, in the OCSP and 7.0% (1.6 to 12.4) and 5.9% (1.0 to 10.9) in the OXVASC. The definition A risk of recurrence was particularly high after partial anterior (22.9%,17.5 to 28.2) and posterior (19.5%,13.0 to 25.9) circulation strokes. CONCLUSIONS: The 3 most widely used definitions of recurrent stroke yield markedly different 90-day risks. We suggest that, where possible, definition A be adopted as the standard to avoid underestimation of risk and to allow valid comparison of different studies.